Formation Mechanism Of The Self-ordering Process Of Anodic Porous Alumina

In this paper, the porous anodic alumina (PAA) was produced by anodization in different electrolytes. The effects of experimental conditions, such as pre-treatment of alumina surface, time, temperature, voltage, electrolyte and concentration on the self-ordering process of anodic porous alumina were studied systematically by the ways of Voltage-time (V-t) curves and SEM. On the base of that, the formation mechanism and the self-ordering process of anodic porous alumina were studied thoroughly. Finally, a new self-ordering model of plum blossom patterns was proposed.In order to know the effect of pre-treatment of alumina surface on the self-ordering of PAA, Al surface processed by three different pre-treatments and the self-ordering statement of PAA were analyzed by SEM, and the process of self-ordering of PAA was also studied through V-t curves. Then the other effect of anodic time on self-ordering process of PAA was studied through analyzing SEM photos of PAA formed in different time in H3PO4 solution, at the same time the effect of ethylene glycol on self-organization was studied through analyzing SEM photos of PAA formed in ethylene glycol solution. Beside that, another effect of anodic temperature on self-organization was studied through comparing shapes of PAA formed in H3PO4 solution in the different temperatures. The effect of voltage and current density on self-organization was studied through analyzing SEM images of PAA formed in different voltages and current densities. At last, the effect of electrolyte species and concentrations on the self-organization was studied by analyzing the surface morphologies of PAA formed in sulfuric acid, phosphoric acid, and oxalic acid, respectively.For the uncertainty of the essence of the self-ordering process of PAA and the current status that the acidic electricfield-assisted dissolution theory can not give a reasonable explanation for the plum blossom patterns on the surface of PAA, a new self-ordering model of plum blossom patterns based on oxygen bubble mould was proposed. The formation of ordered nano-channels and the essence of self-organization are the result of the oxygen evolution in the nano-channels. The formation of self-ordering structure and the growth of oxide film are related with the rate and size of the oxygen evolution in the nano-channels.